2.1. Introduction
A variety of pyrolysis technologies are being investigated for producing liquid intermediates from biomass that can be upgraded into hydrocarbon fuels. Traditional biomass flash pyrolysis processes have demonstrated a roughly 70% liquid product yield; however, this pyrolysis oil product has limited use without significant stabilization and upgrading. Unfortunately, the physical and chemical properties of fast biomass pyrolysis oils make them unsuitable for integrating into existing petroleum refineries. Undesired properties of conventional pyrolysis oil include 1) thermal instability and high fouling tendency; 2) corrosiveness due to high organic acid content (pH 2.2 to 2.4, typically); 3) immiscibility with refinery feedstocks due to high water and oxygenates content; and 4) metals (K, Na, and Ca) and nitrogen content, which foul or deactivate refinery catalysts.
KiOR Technology (e.g., PCT Publ. No. WO 2011/096912, O'Conner et al.) focuses on a biomass pretreatment process that produces a composite material that is a blend of finely ground biomass reacted with a solid base catalyst, like clay or hydrotalcite, at 200 to 350° C. They disclose the following: (i) Pretreatment Options; (ii) A moderate temperature torrefaction step (roasting or toasting) to dry the material and grind it before it is mixed with the solid base catalyst; (iii) Soaking the biomass in an alkali carbonate aqueous solution to impart inorganic base catalyst into the biomass; (iv) Biomass catalytic cracking (BCC) is an acid catalyzed cracking and deoxygenation process at 350° C. to 400° C.; (v) Fast fluidized or entrained bed reactor; or a transport reactor, much like fluid catalytic cracking; (vi) Regenerate catalyst at temperatures up to 800° C. to remove coke and provide process heat; (vii) Resulting biocrude is upgraded to gasoline and diesel and the char and coke by-products are oxidized for process heat.
U.S. Pat. Publ. No. 2009/0227823 (Huber et al.) described catalytic pyrolysis using zeolites that are unpromoted or are promoted with metals. The pyrolysis was carried out at a temperature of 500 to 600° C. and a pressure of 1 to 4 atm (approximately 101 to 405 KPa) to produce a highly aromatic product with apparent high coke yields and low liquid yields.
PCT Publ. No. WO 2009/018531 (Agblevor) described the use of catalytic pyrolysis to selectively convert the cellulose and hemicellulose fractions of biomass to light gases and leave behind pyrolytic lignin. The methods used H-ZSM-5 and sulfated zirconia catalysts in a fluidized bed reactor to obtain an overall bio-oil yield of 18-21%.
GTI's IH2 process (hydropyrolysis followed by hydroconversion then C1-C4 gas reforming to supply hydrogen)(e.g., U.S. Pat. Publ. No. 2010/0256428, Marker et al.) is directed to a high pressure system with a pressure range from 100-800 psig (for hydropyrolysis, hydroconversion and gas reforming).